Plating as a method of forming films on substrates is becoming increasingly common in semiconductor manufacturing. More specifically, electroplating is becoming recognized as a cost-effective method for forming conductive films, such as copper on semiconductor substrates. FIG. 1 includes a cross-sectional view illustrating portions of a plating system 10. The plating system 10 includes a chamber 11, a plating solution 19, a plating solution inlet 111 and a plating solution outlet 113, a cup 12, a ring thief 17, a diffuser 13, an anode 14, a cathode 15, and a substrate 155 coupled to the cathode 15. The cathode 15 additionally includes a turntable assembly 151 and clamps 153. During operation of the of the plating system 10, current flows through the plating solution between the anode 14 (positive electrode) and the cathode 15 (negative electrode), and metal ions in the solution are reduced to metal atoms that deposit onto the substrate 15. At the anode, an oxidation reaction occurs that replenishes the plating solution with metal ions reduced at the cathode.
Currently, no commercially viable methods exist for measuring the plating solution's current density. A pH probe can measure the concentration of ionic species in the plating bath, however, it cannot measure current density. A current measuring probe can manually be manipulated within the plating solution, but this method has disadvantages. First, the probe measures only specific singular locations within the plating solution. These points correspond to only small areas of the substrate. Second, the probe cannot be used when processing production substrates because it interferes with and undesirably impacts the plating deposition process. Therefore, this prior art method is capable of only being used with non-production (dummy) wafers. Finally, because the probe is continually being removed and reintroduced into the bath, particle generation may be of concern. Particles and contaminants introduced by the probe can cause a number of problems that degrade the quality of the plated film.